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A randomized controlled pilot study of a brief web-based mindfulness training
BMC Psychiatry 2011, 11:175 doi:10.1186/1471-244X-11-175
Tobias M. Gluck ()
Andreas Maercker ()
ISSN 1471-244X
Article type Research article
Submission date 25 July 2011
Acceptance date 8 November 2011
Publication date 8 November 2011
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A randomized controlled pilot study of a brief web-
based mindfulness training

Tobias M. Glück
1, 2
*, Andreas Maercker
2

1
University of Vienna, Faculty of Psychology, Institute of Clinical, Biological and
Differential Psychology, Liebiggasse 5, A-1010 Vienna, Austria,
2

Division of Psychopathology and Clinical Intervention, University of Zurich,
Binzmühlestr. 14/17, 8020 Zurich, Switzerland
* Corresponding author
Email addresses:
TMG:
AM:


Abstract
Background
Mindfulness has been shown to be effective in treating various medical and mental
problems. Especially its incorporation in cognitive-behavioural interventions has
improved long-term outcomes of those treatments. It has also been shown, that brief
mindfulness-based trainings are effective in reducing distress. There have been few
web-based interventions incorporating mindfulness techniques in their manual and it
remains unclear whether a brief web-based mindfulness intervention is feasible.
Methods
Out of 50 adults (different distress levels; exclusion criteria:
<
18 years, indication of
psychotic or suicidal ideation in screening) who were recruited via e-mail and
screened online, 49 were randomized into an immediate 2-weeks-treatment group (N
= 28) or a waitlist-control group (N = 21), starting with a 2-week delay. Distress
(BSI), perceived stress (PSQ), mindfulness (FMI), as well as mood and emotion
regulation (PANAS/SEK-27) were measured at pre-, post- and 3-month follow-up
(3MFU). Intention-to-treat analyses using MI for missing data and per-protocol
analyses (≥50% attendance) were performed.
Results
26 participants of the treatment group completed post-measures. Most measures under
ITT-analysis revealed no significant improvement for the treatment group, but trends

with medium effect sizes for PSQ (d = 0.46) and PANAS
neg
(d = 0.50) and a small,
non-significant effect for FMI (d = 0.29). Per-protocol analyses for persons who
participated over 50% of the time revealed significant treatment effects for PSQ (d =
0.72) and PANAS
neg
(d = 0.77). Comparing higher distressed participants with lower
distressed participants, highly distressed participants seemed to profit more of the
training in terms of distress reduction (GSI, d = 0.85). Real change (RCI) occurred for
PSQ in the treatment condition (OR = 9). Results also suggest that participants
continued to benefit from the training at 3MFU.
Conclusion
This study of a brief web-based mindfulness training indicates that mindfulness can
be taught online and may improve distress, perceived stress and negative affect for
regular users. Although there were no significant improvements, but trends, for most
measures under ITT, feasibility of such a program was demonstrated and also that
persons continued to use techniques of the training in daily life.
Trial Registration
German Clinical Trials Register (DRKS): DRKS00003209
Background
In recent years mindfulness has been found to be beneficial in various health related
contexts [1, 2]. It can be described as a form of mental training [3] where focus of
attention is directed to present moment experiences in an open, curious and non-
judgemental manner [4]. The technique to enter present moment experiences is
usually the focus on breath or body sensations [5]. It is also important to note, that
mindfulness is not restricted to formal meditation and can be incorporated in everyday
activities [6]. It is however, not to be understood as a simple relaxation technique [7].
Most mindfulness trainings require participants to invest substantial amounts of time
and discipline such as Mindfulness Based Stress Reduction (MBSR) [4]; however,

short mindfulness-trainings lasting from a couple of days up to 4 weeks have also
been reported effective in terms of mindfulness and distress reduction [8-12] and there
is no evidence that shortened versions of mindfulness trainings are less effective [13].
Mindfulness has been described as third wave in cognitive-behavioural interventions
[14] and is successfully incorporated in different cognitive-behavioural oriented
treatments, e. g. for relapse prevention in depression [15]. With its incorporation into
cognitive behavioural manuals, mindfulness is now also used in some web-based
interventions as component in cognitive-behavioural treatment programmes for a
variety of conditions [16-20]. Medium to large effect sizes have been reported in a
programme for irritable bowel syndrome [18] and for depression [19]. Effects
remained in a 6-month follow-up for the depression programme [19] and after 1 ½
years for the irritable bowel syndrome study [21].
Generally for psychotherapeutic web-based treatments, medium effect sizes have been
reported in meta-analyses on different web- and computer-based interventions [22-
24]. Additionally, programmes with therapist contact seem to yield higher effect sizes
than programmes that are self-guided [23, 25]. However, to our knowledge there has
been no study published focusing exclusively on the effectiveness and feasibility of a
web-based mindfulness intervention. It remains unclear whether a programme
exclusively consisting of mindfulness techniques is effective.
We wanted to evaluate whether a brief web-based mindfulness training could be
delivered effectively via the internet for adults with different distress levels (ranging
from lower to higher). We expected that the regular use of the training would have
positive effects on distress and perceived stress, increase mindfulness, and improve
emotion regulation and mood. We were also interested whether participants would
continue to use the techniques, after the training had ended, and that beneficial effects
on mindfulness and other measures would persist.
Methods
Participants
Participants were recruited in February 2010 over the internet by a short information
e-mail containing a link to the official homepage at the University of Zurich. E-Mails

were sent out to members of a students’ club, faculty of both universities and
employees of three companies (a car-dealership, a broadcasting station and a
healthcare consulting company), asking to forward the information on the study to
persons who might be interested in participating. They were also offered to participate
themselves. These initially contacted persons (N=98) in different occupational
settings were chosen in order to reach a broader spectrum of educational levels and
age-groups of potential participants. Approximately 400 persons received the
information via e-mail.
On the information homepage persons could give consent to potentially participate
and to be forwarded to the training’s log-on and registration homepage, hosted by the
University of Vienna. The study was conducted according to the ethical regulations
for clinical trials of Austria and Switzerland. It was approved by the departments of
psychology at both universities. 50 persons registered and completed the screening.
One person exceeded cut-off in the screening and was excluded from the study before
randomization, as depicted in Figure 1.
Persons aged under 18 years, or with indication of a psychotic disorder or suicidal
ideation in the screening were excluded. Furthermore, persons were informed before
they registered for the screening that they could not participate when they were
currently pharmacologically or psychotherapeutically treated for a mental disorder or
suffering of substance dependence. Persons indicating psychotic experience and/or
suicidal ideation in the screening were contacted with information on counselling
centres. Persons with higher distress (at least one of the nine screening scales
exceeding a T-value of 63) were included in the study for later subgroup comparisons.
They were informed, that they had indicated higher distress and were supplied with
information on counselling centres as suggested in the manual [26].
Power was calculated using the software G*Power [27]. The power calculation was
based on previous meta-analyses and individual research with a similar design on
mindfulness interventions and distress reduction as well as effects of web-based
interventions. Thus we expected a medium effect size between d = 0.50–0.70. With p
≤ .05 (two-tailed) and power of a .80, in total 50 participants were required.

Procedure
Using single-case randomization with previously created random number lists
(assignment to even vs. uneven numbers), 49 persons received a standardized e-mail
with information regarding their group-assignment within a day after they had
completed the screening. We chose this approach to minimize information delay
regarding the beginning date of the training. Due to our limited financial resources it
was not possible to automatize the screening and randomization procedure within the
program. However, this procedure resulted in unequal group sizes with 28 persons in
the treatment condition and 21 persons in the waitlist-control group, who started with
a two-week delay after the treatment group had finished the training.
Sociodemographic characteristics of groups are presented in Table 1. Participants in
the treatment group were assessed at baseline and after the last session of the training.
Follow-up at 3 month (3MFU) was completed by participants from both groups, as
displayed in Figure 1. All questionnaires were completed online. The procedure of the
training and time of measurement is depicted in Figure 2.
Measures
Internal consistencies in our sample matched those reported in the manuals of the
instruments (Table 2).
General distress.
The global score (GSI) of the German Brief Symptom Inventory
(BSI) [26], the 53 item version of the Symptom Checklist-90-R, was used to assess
the general distress of participants.
Perceived stress.
The subjective level of stress was assessed with the German 20-
item version of the Perceived Stress Questionnaire (PSQ) [28]. The PSQ assesses the
subjective level of stress on 4 dimensions: worries, tension, joy and demands. It also
delivers a total score of the subjective stress level. It does not rely on a specific
stressful situation. Items are rated on a scale from 1: almost never, 2: sometimes, 3:
often, and 4: usually. The questionnaire was validated in a large German speaking
sample consisting of different patient groups and healthy adults.

Mindfulness.
To measure changes in mindfulness the German 14-item version of the
Freiburg Mindfulness Inventory (FMI) was administered. Originally designed to
measure changes of mindfulness during meditation retreats, it appears to be equally
suitable for participants without meditation experience [29]. The short form shows
good psychometric properties and items are rated on a scale from Rarely,
Occassionally, Fairly often, to Almost always regarding their experiences with
mindfulness. The short form is assumed to measure one general factor of mindfulness
and thus a total score is calculated.
Emotion regulation and mood.
To evaluate improvements in mood and different
facets of emotion regulation skills the EMO-CHECK/SEK-27 [30] was used. It
comprises two parts. The first part (EMO-CHECK) contains the 20 items of the
Positive Affect Schedule Negative Affect Schedule (PANAS) [31] assessing two
dimensions of negative affect and positive affect (further denoted as PANAS
neg
and
PANAS
pos
). In the second part (SEK-27) participants rate on 27 items (never to
almost always) their competences of emotion regulation. Results may be interpreted
on a general score.
Assessment of training perception.
After each daily session participants answered
4 questions regarding their level of stress and how they had experienced that day’s
exercise. These questions were used to calculate the number of days they participated.
At the end of the training participants were asked 13 questions, how they liked the
training, whether they were able to use the techniques and about design and usability.
Questions were rated from -3 to 3 representing total disagreement and total
agreement.

There were also 13 questions administered at the 3MFU which asked whether
participants still practiced mindfulness exercises, when they used them and whether
they were able to integrate mindfulness in their daily routine.


Intervention
After randomization persons received an e-mail with general instructions and details
on the training. The training always started on a Monday to ensure, that all
participants would have equal conditions regarding weekdays. The training duration
was 13 days and consisted of two modules. Each module lasted for 6 days with 20
minute-units per day. The modules were unlocked consecutively, and persons
participated from Monday to Saturday.
All participants received standardized information and reminder-e-mails at the
beginning of the training, after the first week (reminder for the second module), and at
the end of the second module (reminder for post-test measures). Participants could
also contact us via a contact-form on the homepage for technical assistance. Beyond
that the training was self-guided without personal contact.
The training consisted of audio files, a flash animated exercise and written text. In the
first module participants listened to an audio file with guided mindfulness exercises
while being shown a neutral background-picture of pebbles on a white ground.
Techniques included awareness of body sensations; attention to breath and acceptance
of upcoming emotions [4, 32]. In the second module participants were shown a blue
sky. A cloud moved slowly across the sky, when pressing the spacebar once. They
were instructed to practice the techniques learned in module 1 and when being
disturbed by distressing thoughts, feelings or sensations, to label these cues non-
judgementally (e.g. when feeling angry, to acknowledge it by simply labelling the
internal image with “anger”) and imagine placing them on the cloud, watching it
wandering out of sight. Participants were instructed to press the key in full awareness,
also being a marker to focus again on their breath or body sensations. This exercise
was designed to support affect labelling and letting go, and was adapted from dialectic

behavioural therapy [33].
Statistical Analysis
Intent-to-treat analyses (ITT) were conducted on all participants who enrolled in the
training and completed questionnaires at pre-test regardless of the number of days
they used the training. All participants who filled in questionnaires at pre-test and
dropped out in between were included using multiple imputation (MI) with 5
imputations for missing variables [34, 35].
For per-protocol analyses only persons who participated on at least 6 days of the
training and completed questionnaires at both times (pre- and post-test) were included
in this analysis. This algorithm also assured that persons had participated in both
weeks.
For pre–post-test changes, 2x2 repeated measures ANOVAs with time (pre–post-test)
as within-subject variable and group as between-subjects variable were performed.
For changes in the treatment group from post-test to follow-up, paired t-tests were
computed. Effect sizes for main analyses are presented in Cohen’s d. Effect sizes for
paired t-tests were calculated with Dunlap et al.’s formula for Cohen’s d [36].
Correlations (two-tailed) were also calculated with standardized response means [37]
to analyze whether there were similarities to reported associations between FMI and
other measures [29]. We also conducted mediation analysis according to Baron and
Kenny [38] for daily exercise ratings for later outcome.
We calculated Reliable Change Indices (RCI) [39] to detect real changes in terms of
improvement and deterioration. RCIs allow assessing whether a participant displays a
real change with a probability of p ≤ .05 when RCI-cut-off (±1.96) is exceeded.
Please note that this is only an indicator of real, but not necessarily clinically
significant change [40]. Odds Ratios (OR) were calculated regarding favourable
outcome in the treatment group. For 0-cells the conservative modified maximum
likelihood estimate (MMLE) approach suggested by Gart and Zweifel [41-43] was
calculated for ORs and confidence intervals.
All statistical analyses were computed at p ≤ .05, two-tailed, using PASW Statistics
17 (SPSS Inc., Chicago).

Results
Attrition rate.
Of the 49 persons who were eligible to participate, 44 (89.8%) filled in
questionnaires at post-test. 27 persons (55.1%) also responded for the 3MFU. In the
treatment group 64.3% (18 persons) participated for 6 or more days of the training
over both weeks and 26 persons filled in questionnaires at post-test. 6 participants did
not continue their practice in the second week of which two could not be reached for
post-test. Participants with higher baseline levels of distress did not drop out more
often than participants with lower baseline levels of distress. In the waitlist-group two
persons dropped out after randomization and before pre-test (one person entered a
correct, but inactive e-mail-address, the other person asked to be excluded for
personal reasons). Participant flow is presented in Figure 1.
Pre-treatment evaluation
Baseline differences for psychological parameters were analysed using independent
group t-test, and showed statistically insignificant, but small to medium effect sizes
for most measures. There was a significant difference between groups at baseline for
positive affect with a medium effect size (Table 3). Levels of distress at pre-test in
terms of T-Value means in both groups were statistically not different from
population means described in the manual and a more recent validation study in a
representative sample of the German population for the SCL-90-R [44]. It is also
important to note, that irrespective of group, participants who completed grammar
school (F (3, 43) = 3.83, p = .016), and those with little meditation experience had
higher levels of distress (n.s., F (3, 43) = 2.27, p = .094) compared to other
participants.
Intent-to-treat analyses
Analysis suggested that data were missing completely at random (MCAR), X
2
Little
=
30.52, p = .591.

Measures of distress—GSI and PSQ.
PSQ showed a non-significant, but medium
interaction effect, F (1, 45) = 2.64, p = .111, d = 0.46 [-0.13, 1.05], and a significant
main effect for time, F (1, 45) = 4.19, p = .047. For GSI there was no significant
interaction effect, F (1, 45) = 0.07, p = .794, d = 0.08 [-0.50, 0.66], and no significant
main effect for time, F (1, 45) = 0.75, p = .391. Table 4 shows, that there was no
further decrease in GSI, and a small, but non-significant effect for PSQ, d = -0.35, in
the time after the training.
Mindfulness—FMI.
FMI showed a non-significant, but small effect for time–group
interaction, F (1, 45) = 1.08, p = .304, d = 0.29 [-0.30, 0.88], and a significant main
effect for time, F (1, 45) = 7.16, p = .010. Inspection of Table 4 shows a small effect
for further increase in FMI from post-test to follow-up, d = 0.32.
Emotion regulation and mood—SEK-27 and PANAS.
For SEK-27 there was no
interaction, F (1, 45) = 0.02, p = .88, d = 0.05 [-0.53, 0.63], and no effect for time, F
(1, 45) = 1.31, p = .258. PANAS
neg
showed no significant time–group interaction, F
(1, 45) = 3.69, p = .061, but with a medium effect, d = 0.50 [-0.09, 1.09], and a
significant main effect for time, F (1, 45) = 14.24, p = .000. There was no significant
effect for SEK-27 and PANAS
neg
from post-test to follow-up (Table 4). PANAS
pos

yielded no significant time–group interaction, F (1, 45) = 0.07, p = .794, d = 0.08 [-
0.50, 0.66], and no main effect for time, F (1, 45) = 0.322, p = .573. However, there
was a significant, medium effect for the time after the training to follow-up, d = 0.43
(Table 4).

Per-protocol analyses
n was 18 for both groups. GSI showed no significant interaction, F (1, 34) = 0.54, p =
.469, d = 0.29 [-0.30, 0.85], and no significant effect for time, F (1, 34) = 2.05, p =
.162. PSQ yielded a significant interaction effect, F (1, 34) = 5.14, p = .030, d = 0.73
[0.13, 1.33], and a significant effect for time, F (1, 34) = 4.69, p = .037. FMI
displayed a non-significant, but small interaction effect, F (1, 34) = 1.47, p = .234, d =
0.38 [-0.21, 0.97], and changed significantly over time, F (1, 34) = 6.41, p = .016.
SEK-27 showed no interaction, F (1, 34) = 0.52, p = .478, d = 0.24 [-0.34, 0.82], and
no significant main effect for time, F (1, 34) = 3.16. PANAS
neg
showed a significant
time–group interaction, F (1, 34) = 7.75, p = .009, with large effect, d = 0.77 [0.17,
1.37], and significant effect for time, F (1, 34) = 18.61, p = .000. PANAS
pos
displayed
trends with medium effects, but no significance for interaction, F (1, 34) = 2.84, p =
.101, d = 0.56 [-0.03, 1.15], nor time, F (1, 34) = 2.61, p = .115.
Ancillary Analyses
Subgroup analyses with highly distressed participants.
This subgroup-analysis
(n = 26) was conducted only with participants of the treatment group (pre–post-test
)
.
We compared participants with higher distress (n = 12, we defined higher distress as
exceeding a T-value of 63 in any of the nine scales) against participants with lower
levels of distress (n = 14) to see whether there was a difference in the effect of the
training for persons with initial higher levels of distress. We computed 2x2 repeated
measures ANOVAs. The groups did not differ in their initial FMI total score, t (26)
=0.52, p = .703, and there was also no difference in the amount of change of FMI
between the two groups, t (24) = -0.39, p = .608. There was no significant time–group

interaction effect for PANAS
neg
F (1, 23) = 0.03 p = .877, d = 0,05, and PSQ, F (1,
23) = 1.01, p = .325, d = 0.35. There was a significant and large time–group
interaction effect for GSI, F (1, 23) = 4.56, p = .043, d = 0.85, and no significant main
effect for time, F (1, 23) = 1.29, p = .268, d = 0.42. On average highly distressed
individuals reduced their GSI score by 6 T-values (Table 5).
Individual indicators of change.
To evaluate improvement and deterioration we
calculated RCIs [39] for the different measures. For PSQ, 9 persons in the treatment
condition showed significant real change versus 1 person in the waitlist group
(X
2
=5.12, p=.024, OR=9.01). All other measures showed no significant difference
between groups in terms of individual improvement (Table 6).
Correlations of outcome measures and possible mediation.
Negative coefficients
for standardized scores of GSI, PSQ and PANAS
neg
indicate improvement. For
analysis data from treatment group and waitlist (after participating in the training)
were combined (N = 35), and controlled for group. We found significant correlations
between FMI and PSQ, r = 68, p = .000, GSI, r = 49, p = .004, and for PANAS
neg
,
r = 44, p = .009, for pre–post-test. For post-test to follow-up, association of FMI
with GSI and PSQ remained, but not for PANAS
neg
¸ but there was also a strong
association between FMI and SEK-27, r = .57, p = .003, which was negligible in pre–

post-test. Mediation analysis [38] did not show any mediation effects of daily exercise
ratings on post-test outcome; however, daily rating of engagement in exercise
correlated with PANAS
pos
, r = .43, p = .009.
Subjective benefit and long-term use of training.
Directly after the training 73.5%,
and at the 3MFU 66.6% of the participants stated that they found the training to be
beneficial and 70.3% had the feeling that the training had helped them regarding their
inner balance and wellbeing. 45.7% of participants reported that the cloud used in the
second week had helped them letting go. 77.2% would recommend the web-based
mindfulness training. At 3MFU over 50% of the participants reported continued use
of mindfulness techniques when they wanted to calm down in daily live. 25%
reported to still regularly practice mindfulness exercises.
There were medium, but non-significant correlations between GSI and integration of
exercises into daily routine, r = 34, p = .101, and also for use of the cloud exercise
from the second week to support letting go of negative or strong emotions (CLO), r =
32, p = .124. There was a significant relationship between PANAS
neg
and awareness
of self and emotions, r = 41, p = .045. We observed medium, but non-significant
associations of PANAS
neg
with CLO, r = 31, p = .138, and for stating that the
training had provided a good introduction to mindfulness techniques r = 39, p =
.057.
Discussion
In this randomized controlled pilot study effects of a brief web-based mindfulness
training on distress, perceived stress, mindfulness, mood and emotion regulation were
investigated. Trends with medium effects in ITT and larger effects in per-protocol

analysis suggest that a web-based mindfulness training may be effective in reducing
perceived stress and improving negative affect.
In ITT we found medium, but non-significant effects for perceived stress (PSQ) and
negative affect (PANAS
neg
)
. Interaction effects might have been influenced by
baseline differences between groups, increasing overall variance. For mindfulness
(FMI) and emotion regulation (SEK-27) there were non-significant, but small effects.
Otherwise there were no trends or significant interaction effects in the ITT-analyses.
Despite methodological concerns [45], per-protocol analyses were performed, because
we were also interested in the effects of the training when used regularly. The per-
protocol analyses included persons who participated at least 50% of the training. This
criterion was chosen, because it included persons who participated in both training
modules. It has been postulated that only regular practice will result in changes of
mindfulness [4]. This also corresponds with study results on neurobiological changes
related to mindfulness exercise [46]. With persons participating at least for 6 days, the
training showed to be effective for perceived stress (PSQ) and for negative affect
(PANAS
neg
)
with larger treatment effects, and trends with medium effects for positive
affect (PANAS
pos
)
. Effects for PSQ are similar to stress reduction effects in a face-to-
face mindfulness training in a community samples [47].
In most studies using the BSI as a measure of distress, significant changes are
reported [48]; however, this was not the case in our study, with the exception of PSQ.
In this respect it must be taken into consideration that the PSQ, which showed a

medium effect in ITT and larger effect for per-protocol, is related to daily hassles and
stress perception, while the BSI asks for symptom distress. Although there has been
no evidence that shorter mindfulness trainings are less effective in reducing distress
[13], it seems possible that subjective changes in distress were noticed only by those
with higher initial levels of GSI. When conducting subgroup analyses for the
treatment-group, participants with higher GSI at the beginning of the training reduced
GSI scores more than participants with lower initial GSI. Higher distressed persons
reduced on average by 6 T-values. It is also interesting to note, that current literature
states that mindfulness techniques have been particularly helpful in distressed
populations with medium to large effects for distress reduction [9].
Yet, it must also be kept in mind that persons with high levels of distress might be
attracted by such trainings and thus expectations regarding the programme might
account for some of the reduction in the distress score [49]. This pattern would also be
expected for mindfulness outcome; on the other hand, participants with high distress
levels did not increase their level of mindfulness in a different way than participants
with lower levels of distress. Although mindfulness has been previously reported to
mediate positive effects on psychological well-being [50] and perceived stress
reduction[51], data in this study did not show these mediating effects, but there were
some associations between the measures. Hence, we cautiously assume that reduction
effects in maladaptive psychological parameters are related to positive changes in
mindfulness. Furthermore we found expected correlations, and—if not significant—
trends, between mindfulness (FMI) and the other measures. These correlations have
also been reported in other studies [29, 52-54].
In general, when analysing measures for real change as defined by Jacobson and
Truax [39] we found that persons in the treatment condition were 9 times as likely to
report a positive change in PSQ than participants in the control group. With the other
measures we were not able to detect significant differences between the groups.
One of the purposes of the training was that persons would learn mindfulness
techniques in a structured way to use them “offline” when the web-based training
finished. This assumption was supported by small to medium effects for PSQ, d = -

0.35, FMI, d = 0.32, and PANAS
pos
d = 0.43, from post-test to follow-up.
Programme acceptance and satisfaction was high for this web-based training. Despite
findings that self-guided web-based trainings and interventions seem to yield smaller
effects than programmes in which therapists or instructors are included [22] this
programme showed large effects on perceived stress for persons who regularly
engaged in the training.
Although it is reported that attrition rates are a problem in web-based interventions
[22] this was not the case for the treatment group between pre- and post-test. On the
other hand, drop-out rates for the waiting-list group during training were far higher
than in the treatment group, suggesting that the delay of training might have caused
higher attrition rates in this group. This was contrary to findings of other studies
incorporating a mindfulness component [19].
With the exercise introduced in module 2 a new form of interactive mindfulness
exercise was tested. The exercise was inspired by Linehan’s [33] cloud exercise, in
which persons imagine to place distressing sensations or thoughts on a cloud,
watching it passing by. It was taken care that this did not act as vigilance task
paradigm [55], but as a support for the mindfulness aspect of letting go [56]. It was
expected that this kind of affect labelling would mitigate emotional distress by
supporting affect labelling in a non-judgmental manner. There were medium, but non-
significant associations between a greater reduction of PANAS
neg
and GSI with the
use of the cloud technique in 3MFU. Also, when participants stated that they felt more
aware of themselves and their emotions since they participated in the training, this
was significantly associated with changes in PANAS
neg
. This is also supported by
recent neurobiological studies on reduced amygdala response to emotional cues after

affect labelling [57] also indicating that this mechanism is related to mindfulness
exercise [58]. As the exercise was designed without spoken guidance, participants
reported this to be more difficult.
Limitations
The conclusions drawn from the results are limited by the heterogeneity of the data
and also by group-differences in baseline measures with small to medium effect sizes.
Graphical analysis of the data suggested, that this heterogeneity and baseline
differences might have led to significance of some main time effects and non-
significance of interaction effects in the analyses. A source of bias might also have
been the recruitment of participants with different levels of initial distress, which
could be responsible that interaction effects in GSI and FMI did not show
significance. Another limitation was a missing control group in 3MFU, which should
be addressed when conducting a larger scale study. Also the randomization procedure,
using single-case randomization resulting in unequal sample sizes posed another
limitation together with the limited power due to the small sample size.
Further limitations to generalizability are the high proportion of female participants,
the high proportion of persons with academic background and the reliance on self-
report. Especially education has been found to have a mediating influence on several
aspects of mindfulness [50]. There has also been the claim, that mindfulness should
be measured with other means but self-report measures for better validity [29]. As
with most exercises and interventions offered online, it was not possible to control
whether participants stayed in front of the screen and performed the exercises or did
something different and simply returned after twenty minutes to log out. This
however, will remain a problem with most web-based interventions [59].
Conclusions
Although there were some limitations regarding the recruited sample and non-
significant effects in ITT-analysis, this web-based, brief mindfulness training reduced
negative affect and perceived stress for persons who participated at least in 50% of the
training. It can also be assumed that a brief, web-based mindfulness programme may
result in similar effects as face-to-face conducted mindfulness interventions [1], when

used regularly. Furthermore, it may present an interesting adjunct to other web-based
treatments.
To our knowledge there were only studies using mindfulness as a component within
larger treatment protocols. It remained unclear, however, whether mindfulness did
contribute to health improvements reported by these studies [18, 19]. With this
training we were able to show, that a brief mindfulness training is feasible over the
internet and effective for some measures, when used regularly. On the other hand,
there was only an indication, but no empirical evidence, that these effects were
mediated by mindfulness.
For future research a better control of adherence and program use will be well
advised. Future research should address the comparison of a web-based mindfulness
programme compared to a web-based relaxation programme (e. g. progressive muscle
relaxation or cognitive based stress reduction), as it has been conducted face-to-face
[9, 47]. In addition, treatment programmes with and without mindfulness components
need to be compared to identify whether mindfulness is a beneficial adjunct for
different web-based treatments. The results of this study are a first step in
investigating the benefit of web-based mindfulness interventions.
Competing interests
'The authors declare that they have no competing interests.
Authors' contributions

TMG wrote the manuscript, designed the training and conducted the statistical
analysis. AM contributed to data analysis and writing the manuscript. AM also
revised the first drafts and the final manuscript. Both authors developed the research
design equally. Both authors approved the final version of the manuscript submitted
for publication.
Acknowledgements
The study was funded by a master thesis scholarship granted by the University of
Vienna. We are very grateful to Dr. Ulrich Tran for his many valuable comments on
the first drafts and his methodological expertise. We also want to thank Dr. Brigitte

Lueger-Schuster for her support during the project.




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